Subnet calculator
Find the network, broadcast address, host range, and mask for any IPv4 subnet.
Type an IPv4 address and choose a prefix, or type both together like 10.0.0.0/16. You can also enter an address followed by a mask, like 192.168.1.10 255.255.255.0.
What the results mean
- Network address: the first address in the subnet, which identifies the subnet itself.
- Broadcast address: the last address, used to reach every device in the subnet at once.
- Usable host range: the addresses you can assign to devices, between the network and broadcast addresses.
- Wildcard mask: the inverse of the subnet mask, used in router access lists and some firewall rules.
How CIDR prefixes work
The number after the slash says how many of the address's 32 bits identify the network. The rest identify devices. A /24 leaves 8 bits for devices, which gives 256 addresses, 254 of them usable. Each step down doubles the size: a /23 has 512 addresses, and a /16 has 65,536.
Special cases: /31 and /32
A /31 has only two addresses and is used for point-to-point links between two routers, so both addresses are usable and there's no broadcast. A /32 is a single address, often used to refer to one specific host in firewall rules.
Last updated October 2026.